モードＩＩとＩＩＩの混合モード条件下における層間剥離の屈曲進展挙動に関する一考察

Abstract

Crack deflection behavior of delamination in composite laminates under general shear mode failure condition was studied by using DNSCB test method. For the specimens with starter cracks at 90°/90° interfaces, delamination crack was deflected at the top and bottom edges in opposite directions due to tensile principal stress in front of the crack. The two delaminations propagated on the inner and the outer neighboring interfaces of the original crack plane. For the specimens with starter cracks at +45°/-45° interfaces, the delamination was constrained in the original crack plane within several milimeters of propagation. The result indicated that the crack deflection was suppressed by intentionally choosing the laminate configuration, that is the fiber orientation, to be parallel to the resultant shear stress at the interfaces. Energy release rate along the crack front was calculated and decomposed to components GST and GSL, which were derived from shear stress components normal and parallel to the fiber on the crack plane, respectively. Positive or negative signed energy release rate G*ST was introduced to identify which side of the two neighboring layers of the interface to be in tension in front of the crack. The value G*ST adequately indicated location and direction of the crack deflection.